Production of refined solvents



May 25, 1943.

J. E. HARVY, 4R 2,319,987

PRODUCTION OF REFINED SOLVENTS Filed Aug.. 14, 1940 JY/L FHA BFHE/N6 //G/ TFM/Eff SUL F0@ PFDUCV/VG- CHA/V55? Patented `May 25, 1943 PRODUCTION OF EEFINED SOLVENTS Jacquelin E. Harvey, Jr., Atlanta, Ga., assignor of one-half to Southern Wood Preserving Company, East Point, Ga., a corporation of Georgia Application August 14, 1940, Serial No. 352,667

1 Claim.

The present invention relates to a process for vthe recovery of Valuable liquids from hydrocarbons.

An object of the invention is the production of refined solvents of lowered corrosivity from hydrocarbons of sulfur content and of higher boiling range.

Another object of the present invention is the production of rened solvents from liquid and solid hydrocarbons of sulfur content.

A more specific object of the present invention is the conversion of tars and fractions thereof characterized by sulfur content, in entirety if desired of the starting material remaining liquid under process conditions, i-nto refined solvents of superior solvency.

Other objects of the present invention will become apparent from the following disclosures.

The tars forming suitable starting materials for the present process are tars and their fractional parts derived from coal and petroleum, including gas and/or gases and are characterized by content of aromatics and sulfur.

Starting materials previously subjected to the action of hydrogen are suitable starting materials.

Starting materials of -t-he present process also include tars of aromatic content from which low boiling fractions have been removed, as for instance tars from which ysolvent oils have been removed. Viewed broadly, lthe starting materials of the present process are tars of aromatic content, fractions of said tar more viscous than the starting material due to removal of low boiling fractions, high boiling fractions and pitches.

Coal tar and fractions thereof will be shown as a starting material of the following examples, but it will be immediately apparent that other tars or fractions thereof of sulfur content serve as suitable starting materials.

Coal tar is a destructive distillate of coal, generally having a preponderance of fractions boil-l ing above 190 C. and a typical specific gravity of 1.120, and in its higher boiling range represents molecular complexes that may be viewed as a multiplicity of ring structures.

To the end that coal tar in substantial entirety remaining liquid under the present process conditions be converted if desired into solvents of the present invention, said molecular' complexes must be progressively or step-wise reduced in size, and, among other things, the present invention is predicated on such teaching.

As far as applicant understands the theory of Vthe present invention, the same is predicated on the following:

First: by depolymerizing the molecular complexes in step-wise fashion they are finally brought down to the rened solvents of the present invention.

Second: that by impressing reaction conditions on said molecular complexes they are converted into solvents whose solvency is directly measurable and/or usable as opposed to the absence of such characteristics in the molecular complexes contained in the starting material, and,

Third: said molecular complexes must be, to conform to the present invention depolymerized under conditions that induce no substantial quantity of normally liquid product that are other than aromatic. By the term substantial aromatcity as used herein and in the appendedl claims is meant that the refined solvents of the present invention are at least substantially 50% aromatic.

Viewed broadly, the present invention provides a process wherein among other things, coal tar or the like, or fractions thereof, characterized by sulfur content, are subjected to the action of hydrogen to lower corrosivity, afterwards to the action of hydrogen under controlled conditions whereby the high molecular .complexes of said starting material are reduced in step-Wise manner `to produce rened solvents of lowered corrosivity and are characterized by lowered and controlled boiling range and directly measurable and/or usable solvency as opposed to the absence of similar characteristics in said molecular complexes'.

The invention will be understood from the following description of illustrative steps comprisi-ng various methods of securing the objects of the invention, when read in connection with the accompanying drawing wherein the gure is a diagrammatic sketch of an apparatus for carrying out a form of the process of the invention and wherein the nature of the step carried out in each chamber and the contents thereof are indi-cated by legend.

Example. Coal tar, specific gravity 1.120 and 3% distilling at 21.0 C. and characterized by sulfur content is treated with hydrogen at '350 C. and 200 atmospheres pressure to lower sulfur content thereby lowering corrosivity, or providing for such in nal product; the coal tar of reduced sulfur content is passed through a high pressure reaction vessel at a temperature of 405 C. and a pressure of 300 atmospheres. Flow of hydrogen is 15,000 cubic feet per barrel tar. The :time of contact is one hour and the catalyst molybdenum oxide. The beneficiated coal tar flowing from the reactor is distilled to an upper limit of 210 C. to recover the refined solvent of lowered corrosivity as a distillate. The residue resulting from said solvent recovery is of a more liquid nature than a comparable cut on the starting material, indicating that the high boiling ends formerly described as including multiplicity of rings had been at least either saturated or partially saturated, thus providing the initial step in the step-wise conversion of substantially the entirety of the tar remaining liquid under process conditions into the refined solvent of lowered corrosivity of the present i-nvention.

The residue resulting from rened solvent recovery may be recycled forconversion to the refined solvent of the present invention.

Thus, under the action of hydrogen while contacting an oxide catalyst, the starting tar under temperature and pressure conditions chosen from in excess of 250 C. and atmospheric, respectively, is converted to refined solvents of lowered corrosivity boiling, as an example, below 210 C., said refined solvents being characterized by substantially 50% aromatic content .or more, and being further characterized by being products produced while step-wise reduction of a multiplicity of rings is being effected; said solvents may be further characterized as being those products fiowing from ring reduction, including reduction in size, wherein said reduction is accom' plished under coordinated time, temperature and pressure conditions that preclude substantial carbonaceous deposition, as for instance 25%; carbonaceous deposition referring to any time or period of the process wherein controls are impressed for multiplicity of ring reduction for final formation of the rened solvent of the present invention.

After formation of the refined solvent of lowered corrosivity of the present invention and removal thereof from the parent and beneciated material, said refined solvent may be fractionally cut as desired, or the cut or cuts may be effected at the time of recovery from the parent material.

Viewed broadly, the present invention provides a process for subjecting tars or fractions thereof boiling substantially above 190 C., characterized by sulfur content and derived from coal, petroleum or gas to the action of hydrogen, as heretofore stated, one or more times, as to induce solvency of usable and/or measurable quality as opposed to the absence of such characteristic in the ring multiples contained in the starting material.

The present invention may be practiced in a discontinuous manner, or in a continuous manner in a high pressure reaction chamber, a series of reaction chambers, a parallelism of reaction chambers including a multiplicity thereof.

By the term beneciated as herein and in the vappended claim is meant the starting material range or ranges of benzene, toluene, xylenc and the various naphthas and plasticizers. Heavy naplithas proposed as solvents are currently available having an end point in the order of 360 C.; the present invention provides for cutting the solvent at any desired point With subsequent fractionation into desired cuts as may be dictated by commercial necessity; residue may be recycled as aforetaught.

The phase condition of the present process is liquid phase and is not that phase that gasifies all starting materials. The term liquid phase .as used herein may not be technically correct, but

is meant to differentiate from processes that gasify all material processed.

The starting materials of the present process are not circumscribed by limitations in carbon content, being merely limited by the nature of tars or fractions thereof available. Tars of more than usual carbon content may be depolarized under less severe conditions at first, with severer conditions progressively applied until maximum reaction conditions are attained.

Many modes of practicing the present invention are possible as will be apparent to those skilled in the art. For instance, tar may be stripped of any percentage of low boiling ends and the residual mass then treated in accordance with the present process to provide the products-refined solvents of lowered corrosivity-of the present invention.

Thus, pitches hard or soft are among the starting materials of the process; also included in the starting materials of the present process are those residual portions of tar, more viscous than the parent material, resulting from removal of low boiling ends therefrom. Viewed broadly, the starting materials of the present process are tars and fractions thereof characterized by sulfur content, and may have been at least once refined as by hydrogen.

High boiling aromatic tars and fractions thereof of sulfur content produced by the petroleum industry are usable starting materials.

Those skilled in the art know that hydrogenations proceed at relatively low pressures, as for instance atmospheres, however, commercial recoveries of the refined solvents of the present process are best effected at elevated pressures, thus the present invention includes use of pressures as high as practicable. The time element of treatment may be as short as one hour, or less; however, tars or fractions thereof of appreciable carbon content may require longer periods, whereby to effect said depolymerization.

The solvents of the present invention are varied in boiling range and may include the ranges of any or all of the following:

Product Boiling range Instead of controlling the process to provide a low boiling point of 78 C., as for instance in the benzol shown, processing may be controlled to produce lower boiling products. Controls of lesser intensity produce solvents of higher initial point, while controls of greater intensity produce solvents of lower boiling points.

The solvent of the present process may be characterized by containing fractions boiling at least 150 C. to 200 C.

Broadly considered, the present process provides a method for converting tars of aromatic content and fractions thereof including creosote, topped tars, stripped tars and various pitches characterized by sulfur content, to refined solvents of lowered corrosivity by the controlled action of hydrogen under conditions that induce no substantial percentage of liquid chain structures or substantial carbon deposits, as above explained.

The catalysts of the present invention are oxides; oxides of metals of the 6th and 8th periodic groups are usable, however, all oxides catalyst may be used. Diicultly reducible oxides are preferred.

In the first cycle of hydrogen action that reduces sulfur content Without substantial solvent increment, said reduction of sulfur may be accomplished in the presence of a catalyst. Catalysts effective in the presence of hydrogen are usable, as for instance the oxides and/or suldes of molybdenum, vanadium, uranium, cobalt, tin, manganese, tungsten, or the like.

In the disclosures herein made the removing of low boiling fractions by gas movement or pressure release is considered the equivalent of distillation.

When reference is made to high molecular complexes contained in the starting material, and when the starting material contains low boiling fractions that are not considered high molecular complexes, it is of course obvious that the high molecular complexes contained in the starting material are to a certain extent depolymerized by the solvent present; in other words, if high boiling fractions of tar including pitches characterized by content of molecular complexes are used as the starting material, said molecular complexes prior to being subjected to process variables may rst be depolymerized with a suitable solvent.

It will be seen that by reduction of sulfur content cf the material under treatment during the first stage of hydrogen action, the oxide catalyst used during subsequent stage or stages is at least partially protected from the effect of the sulfur.

Minor changes may be made in the foregoing without departing from the spirit of the invention.

I claim:

In the production of solvents from a mixture of sulfur-bearing high temperature coal tar fractions, the process which comprises: subjecting said mixture of tar fractions to the action of hydrogen with time, temperature, and pressure conditions so adjusted as to lower sulfur content of said tar fractions; thereafter subjecting said tar fractions of lowered sulfur content to the action of a flow of hydrogen of about 15,000 cubic feet per. barrel material treated, in the presence of a molybdenum oxide catalyst at a pressure of about 300 atmospheres, a temperature in excess of 400 C., and with the time of reaction so adjusted as to reduce molecular complexes in said tar fractions whilst inducing newly formed low boiling fractions preponderantly o-f aromatic nature; and stripping the treated material to provide newly formed low boiling fractions as solvent material.

JACQUELIN E. HARVEY, Je.

CERTIFICATE or CORRECTION.

Patent No. 2,519,987 May 25, 19II5.

- JACQUELIN E. HARVEY, JR.

It is hereby certified that error appears in the printed specification patent requiring correction as follows: Page 2, seoon. column, line 20, for *'depolarized" read --depo1ymerized; and that the said Letters Patent should be read with this correction therein that rdxof the case in the Patent Office.

of the above numbered the same may conform to the reco signed and sealed this 29th day of June, A. D. 19M.

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents. 

